Process for producing solid biomass fuel

Abstract

The present invention relates to a process for producing a solid biomass fuel, as well as a solid biomass fuel produced by said process. Additionally, the present invention relates to a combustion process comprising combusting said solid biomass fuel so as to produce energy.

The invention claimed is: 
     
       1. A process for producing a solid biomass fuel, wherein the process comprises the following sequential steps:
 (i) providing one or more sources of biomass; 
 (ii) pulverizing the one or more sources of biomass to provide a pulverized biomass powder with an average particle diameter (D50) of from 1000 μm to 20,000 μm; 
 optionally, (iii) compressing the pulverized biomass powder to provide a compressed biomass powder; 
 (iv) washing the compressed biomass powder or the pulverized biomass powder with an aqueous wash liquid to provide a washed biomass powder; 
 (v) mechanically dewatering the washed biomass powder to provide a dewatered biomass powder and an aqueous effluent; 
 (vi) drying the dewatered biomass powder to provide a dried biomass powder; 
 (vii) molding the dried biomass powder so as to provide a molded biomass product; 
 (viii) heating the molded biomass product to a temperature of from 160° C. to 420° C. for a time period of from 0.25 to 5 hours so as to provide a solid biomass fuel; and 
 (ix) washing the solid biomass fuel with an aqueous wash liquid. 
 
     
     
       2. A process according to  claim 1 , wherein the one or more sources of biomass comprise, consist essentially of, or consist of corn straw, sesame straw, straw, banana tree, peanut straw, palm empty fruit bunches (EFB), palm fiber, palm shell, bamboo, palm tree trunk,  Calliandra calothyrsus, Acacia mangium, Albizia chinensis, Hevea brasiliensis , rice husk, yam, corn cob, wood, grass or any combination thereof. 
     
     
       3. A process according to  claim 1 , wherein step (iv) of washing the compressed biomass powder or pulverized biomass powder with an aqueous wash liquid to provide a washed biomass powder comprises washing the compressed biomass powder or pulverized biomass powder in from two to ten successive washing stages, wherein each successive washing stage comprises spraying the compressed biomass powder or pulverized biomass powder with the aqueous wash liquid and/or immersing the compressed biomass powder or pulverized biomass powder in the aqueous wash liquid. 
     
     
       4. A process according to  claim 3 , wherein the successive washing stages are performed in a counter current manner whereby aqueous wash effluent from a later washing stage is used as the aqueous washing liquid for an earlier washing stage. 
     
     
       5. A process according to  claim 3 , wherein the aqueous wash liquid is at a temperature of from 5° C. to 160° C. during step (iv) of washing the compressed biomass powder or pulverized biomass powder with an aqueous wash liquid to provide a washed biomass powder. 
     
     
       6. A process according to  claim 1 , wherein the process comprises step (iii) of compressing the pulverized biomass powder to provide a compressed biomass powder. 
     
     
       7. A process according to  claim 6 , wherein the pulverized biomass powder has a moisture content of at least 30% by weight, and wherein after compressing step (iii), the compressed biomass powder has a moisture content of less than 30% by weight. 
     
     
       8. A process according to  claim 1 , wherein step (vii) of molding the dried biomass powder so as to provide a molded biomass product comprises adapting the molding step such that the density of the molded biomass product is controlled, wherein adapting the molding step such that the density of the molded biomass product is controlled comprises controlling the compression ratio of a mold used in said molding step. 
     
     
       9. A process according to  claim 1 , wherein step (viii) of heating the molded biomass product is carried out for a time period of from 0.4 to 2.5 hours, and wherein the step of heating the molded biomass product comprises heating the molded biomass product to a temperature of from 180° C. to 350° C. 
     
     
       10. A process according to  claim 1 , wherein step (viii) of heating the molded biomass product is adapted so as to control the uniformity of the solid biomass fuel, wherein adapting step (viii) so as to control the uniformity of the solid biomass fuel comprises conducting step (viii) in an apparatus in which the molded biomass product is rotated whilst being heated. 
     
     
       11. A process according to  claim 1 , wherein step (ix) of washing the solid biomass fuel with an aqueous wash liquid comprises spraying the solid biomass fuel with the aqueous wash liquid. 
     
     
       12. A process according to  claim 1 , wherein the process further comprises a step of removing dust particles from the solid biomass fuel; and wherein the step of removing dust particles from the solid biomass fuel comprises:
 (a) removing dust particles from the solid biomass fuel with a screen; wherein the screen has a pore size of from 2 mm to 8 mm; 
 (b) removing dust particles from the solid biomass fuel with a screen; wherein a drum sieve is used to as a screening device to remove the dust particles from the solid biomass fuel; 
 (c) wherein the step of removing dust particles from the solid biomass fuel comprises subjecting the solid biomass fuel to vibration, rotation, rolling, or any combination thereof; 
 (d) wherein the step of removing dust particles from the solid biomass fuel comprises subjecting the solid biomass fuel to vibration, and wherein the step of removing dust particles from the solid biomass fuel comprises using a vibrating screen, wherein the vibrating screen has a pore size of from 2 mm to 8 mm; and/or 
 (e) removing dust particles from the solid biomass fuel with a screen; and wherein the step of removing dust particles from the solid biomass fuel is carried out concurrently to step (ix) of washing the solid biomass fuel with an aqueous wash liquid, wherein step (ix) of washing the solid biomass fuel with an aqueous wash liquid comprises spraying the solid biomass fuel with the aqueous wash liquid, and wherein the screen is used to drain the aqueous wash liquid from the solid biomass fuel. 
 
     
     
       13. A process according to  claim 1 , wherein the solid biomass fuel has one or more of the following properties: an ash content of the solid biomass fuel is 15% by weight or less; the potassium content of the solid biomass fuel is 0.2% by weight or less; the nitrogen content of the solid biomass fuel is 2% by weight or less; the chlorine content of the solid biomass fuel is 0.05% by weight or less; the sulfur content of the solid biomass fuel is 0.2% by weight or less; the fixed carbon content of the solid biomass fuel is 40% by weight or less; the volatile matter content of the solid biomass fuel is 15% by weight or less; the internal moisture content of the solid biomass fuel is 1% by weight or less; the received base moisture content of the solid biomass fuel is 6% by weight or less; the calorific value of the solid biomass fuel is 4500 MJ/Kg or more; the bulk density of the solid biomass fuel as determined according to DIN EN 15103 is from 1.0 to 1.4 g/cm 3 ; and/or wherein material derived from biomass is present in the solid biomass fuel in an amount of at least 95% by weight of the total fuel content of the solid biomass fuel; wherein the sulfur content is determined according to DIN EN15289; the nitrogen content is determined according to DIN EN 15104; the fixed carbon content is determined according to DIN EN 51734; the ash content is determined according to EN 14775 at 550° C.; the volatile matter content is determined according to DIN EN 15148; the calorific value is determined according to DIN EN 14918; the chlorine content is determined according to ISO16994:2015; the potassium content is determined according to ISO16995:2015; the received base moisture content of the solid biomass fuel is determined according to GB/T211-2017; and the internal moisture content of the solid biomass fuel is determined according to DIN EN 14774. 
     
     
       14. A process for producing a solid biomass fuel, wherein the process comprises the following sequential steps:
 (i) providing one or more sources of biomass; 
 (ii) pulverizing the one or more sources of biomass to provide a pulverized biomass powder with an average particle diameter (D50) of from 1000 μm to 20,000 μm; 
 optionally, (iii) compressing the pulverized biomass powder to provide a compressed biomass powder; 
 (iv) washing the compressed biomass powder or pulverized biomass powder with an aqueous wash liquid to provide a washed biomass powder; 
 (v) mechanically dewatering the washed biomass powder to provide a dewatered biomass powder and an aqueous effluent; 
 (vi) drying the dewatered biomass powder to provide a dried biomass powder; 
 (vii) molding the dried biomass powder so as to provide a molded biomass product; and 
 (viii) heating the molded biomass product to a temperature of from 160° C. to 420° C. for a time period of from 0.25 to 5 hours so as to provide a solid biomass fuel; 
 wherein the one or more sources of biomass comprise, consist essentially of, or consist of: sesame straw, palm empty fruit bunches (EFB), palm fiber, oil palm tree, banana tree,  Calliandra calothyrsus, Albizia chinensis , rice husk, yam, corn cob,  Pennisetum  sinese Roxb, or any combination thereof. 
 
     
     
       15. A solid biomass fuel derived from one or more sources of biomass, wherein the bulk density of the solid biomass fuel as determined according to DIN EN 15103 is from 1.0 to 1.4 g/cm 3 ; the calorific value of the solid biomass fuel as determined according to DIN EN 14918 is 4500 MJ/Kg or more; wherein material derived from biomass is present in the solid biomass fuel in an amount of at least 95% by weight of the total fuel content of the solid biomass fuel; and wherein the one or more sources of biomass:
 (i) consist of, or consist essentially of sesame straw; 
 (ii) consist of, or consist essentially of palm empty fruit bunches; 
 (iii) consist of, or consist essentially of palm fiber; 
 (iv) consist of, or consist essentially of banana tree; or 
 (v) consist of, or consist essentially of oil palm tree trunk. 
 
     
     
       16. A combustion process comprising the step of combusting a solid biomass fuel in accordance with  claim 15  so as to produce energy. 
     
     
       17. A process according to  claim 1 , wherein washing step (iv) comprises washing the pulverized biomass powder or compressed biomass powder with an aqueous wash liquid via a counter-current washing mechanism, whereby washing step (iv) is carried out in an apparatus comprising a screw adapted to transport the pulverized biomass powder or compressed biomass powder in a first direction through the apparatus; and wherein the apparatus is adapted to receive and transport the aqueous wash liquid in a second direction through the apparatus that is opposite to the first direction such that that the aqueous wash liquid contacts the pulverized biomass powder or compressed biomass powder within the apparatus.